Emerging diseases

Nguyen Tien Dung DVM, PhD.Head of Virology

National Institute for Veterinary Research86, Truong Chinh, Dong Da, Hanoi

EMERGING DISEASE

WHO’s definition: An emerging disease is one that has appeared in a population for the first time, or that may have existed previously but is rapidly increasing in incidence or geographic range

Which are they?

GROUP II - RE-EMERGING PATHOGENS (human only)

Enterovirus 71 Clostridium difficile Coccidioides immitisMumps virus Prion diseases Streptococcus, group A Staphylococcus Aureus Coccidioides immitis

GROUP III – AGENTS WITH BIOTERRORISM POTENTIAL- NIAID – Category A - NIAID - Category B - NIAID - Category C

GROUP I – PATHOGENS NEWLY RECOGNIZED IN THE PAST TWO DECADES (humans only)Acanthamebiasis Australian bat lyssavirus Babesia, atypical Bartonella henselae Ehrlichiosis Encephalitozoon cuniculi Encephalitozoon hellem Enterocytozoon bieneusi Helicobacter pylori Hendra or equine morbilli virus Hepatitis C Hepatitis E Human herpesvirus 8 Human herpesvirus 6 Lyme borreliosis Parvovirus B19 Nipah virus

J Clin Invest. 2004 March 15; 113(6): 796–798.

http://www.who.int/csr/don/archive/disease/en/

WHAT ABOUT VIETNAM?

Human:• Sars (2003)• AI (2003)• Rubella (2005)• Foot, hand and

mouth (2006)• Str. suis (2007)• Cholera (2007)

Animal:• Foot & Mouth

(1995) • AI (2003)• Capripox (2004)• PRRS (blue ear

disease - 2007)

WHY ARE THEY EMERGING?

• Pathogen nature: RNA virus is prone to mutation

• Environment degradation (deforestation, chemical, vectors, wild animals, land use…)

• Population displacement (more contact, rapidity)

• World population increase (food need, hygiene…)

• Resistance to drugs (malaria)

• Industries: prions. Food-born

• …

Virus nature (example)

• RNA viruses: spontaneous mutation 1/1,000 as compared to 1/100,000,000 in DNA

• Mutation due to chemicals• Adaptive evolution (vaccine, new host…)• Re-assortment: AI• Recombination

Phylogenetic relationship of 19 PRRSV CAVs. Letters (A, B, and C) represent the lines of pig passages in which the variant was detected during 367 days of in vivo replication. Lines represent

the distances of sequence divergence from the ancestor (CC-01).J Virol. 2002 May; 76(10): 4750–4763.

Emergence of the AIVH5N1 (1997)Hång K«ng

H9N2 H6N1 H5N1

G1 w312 Gs/Gd

H5N1/97

H?N?

H5N1/2001 H?N?

Y280

H9N2

A B C

H9N2 H6N1 A B C D E H9N2 (Y280)

Virus cóm HKN¨m 2001

N¨m 1997

stop

Qu¸ tr×nh TiÕn

Hãa vi rót Cóm giaCÇm t¹i

Hång K«ng(theo Guam et al, 2002)

PB2PB1PAHA

NPNAMNS

PB2PB1PAHA

NPNAMNS

H5N1 g©y bÖnh t¹i ViÖt Nam(ViÖn Thó y, ViÖn VSDT

vµ §H Hèng k«ng)

A/Gs/Gd/96 (H5N1)1996 -

Do tæ hîp tõ mét vi rót sinh ra nhiÒu vi rót míi

- Newlyidentified viruses

- Advances in virology

- Urban migration

- Population displacemen

t

- Quality of environment

New viruses in global village

2000

1900

1600

17001800

- World population

While the world population soars and the quality of the environment degrades, the number of the newly identified viruses increases. These viruses are the cause of emerging diseases in humans, animals and plants that may have a devastating impact on the world’s health.Source: Havard University Press, 1992

When, where & how?

• More and more frequent . Vietnam: AI, PRRS, Cholera, Dengue, FHMD… only in 2006-2007.

• Where: – Every where e.g. AI, HIV/AID– West Nile in USA– FHMD in Vietnam 2006– ASF in Georgia 2007– …

• How: from a regular basis to a more randomness.

http://www.who.int/csr/don/archive/disease/en/

Summary

• What: Emerging and re-emerging diseases • When and where: Appear each day more and

more frequently (in time) and in any place and few days it can be spread all over the world (in space) . For ex. : SARS

• Why: Convergence theory (it is not due to a single reason). It may be the paying back for the development.

• How: unpredictable.

WHAT WE ARE DOING

• Concept of emerging diseases: 1990’s• Institutional level : three main tasks have been

worked out:– Preparedness Strategies of fighting.– Emerging disease centers– Information network

• Scientist level:– Mathematic modeling– Computer based simulation of the disease (outbreak)– Statistic: to test hypothesis.

Emerging Disease Centers

• Only in industrialized countries• In the developing countries: hindered by the

endemic diseases and resources

The development is a irreversible process (world population, transport…); few factors can be recovered (environment); Emergence

disease apparition is so a going on process; efforts are now focused on monitoring , early detection and control measures.

THE CENTRES

• New techniques of diagnosis and screening (molecular and computer techniques combined) : Real-time PCR , sequencing… (simple & easy to use device + results to satellite and to the centers).

• Systematic surveillance (modern epidemiological approaches)

• Objective: gathering all the data for a prompt processing for an early alerting.

Influenza Diagnostic Technologies

Nucleic Acid Detection:

Nucleic Acid Arrays

• Flow-through arrays • Microarrays,GeneChips

• Nucleic Acid-targeted Liquid Arrays

www.combimatrix.com BioTrove.com

Influenza Diagnostic Technologies

Nucleic Acid Detection:

RT-PCR and qRT-PCR• Single Target and Multiplex• Single tube and 96-well• Wet reagent, lyophilized• Commercial kits (AI, H5)

• Fully-integrated technologies(extraction to result)

Objectives

• New techniques: early detection, pathogen identification and comparison with the previously existed ones.

• Epidemiology: measuring the disease (in time and space), understanding the disease (transmission, reservoir, immunity, treatment…), GIS +environment data. Hence, work out effective measures

The Genomics Program of the Division of Microbiology and Infectious Diseases at NIAID, USA established in 2004.

http://www3.niaid.nih.gov/research/topics/pathogen/default.htm.

Infect. Immun. 2007 July; 75(7): 3212–3219

AN EXAMPLE: H5N1 BIRD FLU

Two main concerns (among many others):

• Virus: is it changed; how much is the change; what does the change mean? Which one is good for vaccine production?

• Epidemiology: Is there human to human transmission? How is it distributed?

Probability of AI Outbreaks based on Logistic Regression Model for 1st AI Epidemic

Provinces

Outbreak probability

0-0.1

0.1-0.2

0.2-0.3

0.3-0.4

0.4-0.5

0.5-0.6

0.6-0.7

Courtesy: DAH -Vietnam

INFORMATION NETWORKS

• Much more in progress due to IT as compared to the establishment of Centres.

• ProMedmail was established in 1993 (ProMED-mail, www.promedmail.org). Disease information in the world is hourly updated.

Summary

• Emerging diseases continue to appear in the world and become a risk for the humans, animals and plants.

• The preparedness to fight the disease is a stake of future of the earth

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